The invention relates to photography and photographic equipment and methods and more particularly relates to a method for detecting encodement filtering.
Optically recorded encodements on photographic filmstrips have long been used to control printing and other functions. U.S. Pat. No. 5,740,479 describes optical encodements and indicates that it is known to use reflected light from the photographic subject or a light directly from a camera light source to provide the illumination for recording the optical encodement. This patent also notes that the use of ambient lighting to write the encodement is subject to the shortcoming that the recorded information can be difficult to distinguish under some lighting conditions.
It is known to prerecord encodements on film before a one-time-use camera is assembled. It is also known to record encodements for selected image frames based upon a camera condition at the time of picture taking. U.S. Pat. No. 6,332,059 combines both practices. A first encodement is prerecorded on the film before assembly and a second encodement is added to selected film frames based on the position of a selection switch. An encodement that applies to all of the images in a film unit can be recorded so as to apply to all frames, rather than being repeated. U.S. Pat. No. 5,761,558 discloses the recording of extensive information on the outside of a film unit in a visible bar code.
Encodements can be placed in various positions. U.S. Pat. No. 6,332,059 discloses placement of optical encodements at film margins adjoining film frames. U.S. Pat. No. 5,587,752 discloses placement of optical encodements laterally next to an image, either within or next to a respective film frame. Japanese patent publication JP 4-328537, published Nov. 17, 1992, discloses a one-time-use camera having a pair of slidable viewfinder masks that move in tandem with a pair of code signal plates for pseudo panoramic and pseudo telephoto final image formats. The code signal plates mask part of the exposure opening when a respective viewfinder mask is in position in the viewfinder. One of the code signal plates is illustrated as having one slot. The other is shown as having two slots. (Image subject matter is visible through the slots.) The final images crop out the pattern made by the code signal plates.
It is also known to record other information within the image area of a filmstrip. U.S. Pat. No. 5,189,467 and U.S. Pat. No. 5,126,773 disclose recording indicia on a mask, which is placed in the film path, and recorded on the image frame at picture taking. U.S. Pat. No. 5,486,885 discloses a similar mechanism that utilizes light from a flash unit in the camera. Japanese patent application 10-161225, published Jun. 19, 1998, discloses a camera that has a dedicated internal light source that shines through a mask to transfer information such as a picture and text onto the image area of a filmstrip. U.S. Pat. No. 2,210,610 discloses a camera that adds different information to each image.
It is well known to use filters in cameras to improve image quality. Japanese Patent No. 3,109,765 discloses that the use of a filter on a one-time-use camera to balance color sensitivity of a film. Japanese patent publication No. 2-78935, published Jun. 18, 1990, discloses a single use camera having a detachable photochromic filter. Japanese patent publication 3-94241, published Apr. 19, 1991, discloses a one-time-use camera having a color correction filter that is switchable to allow use of tungsten balanced film outdoors. Japanese patent publication 63-6428, published Jan. 16, 1988, discloses a one-time-use camera which has a photochromic filter and in which the camera records an unfiltered reference patch to use in determining the state of the filter.
A wide variety of mechanisms are known for moving one or more filters into alignment with and away from a taking lens system. U.S. Pat. No. 6,173,127 teaches a one-time-use camera having a slidable special effects filter. Japanese patent publication JP 11-242257, published Sep. 7, 1999, discloses another camera having a slidable filter. Japanese patent publication JP 2000-235211, published Aug. 29, 2000, discloses a camera having a rotary filter wheel. Japanese patent publications JP 2000-162690, published May 16, 2000, and JP 2001-27773, published Jan. 30, 2001, disclose cameras having a filter wheel offset from the optical axis. U.S. Pat. No. 5,696,996 discloses a camera having a transparent film that moves from roller to roller with the photographic film.
In digital photofinishing, processed images on a filmstrip are scanned, digitally processed, and then printed. With some high-speed equipment, the center portion of a filmstrip is continuously scanned at high resolution. Margins are not scanned, or are scanned at a lower resolution using a different scanner. This makes recognition of optical encodements on filmstrip margins cumbersome, at best. Optical encodements placed in the center portion of the filmstrip remove either image area or the interspacing between frames. The former directly degrades image quality. The latter can degrade the recognition of film frame locations; with film types, such as 35 mm, that do not have perforation defined film frames. One solution to loss of image area is provided by U.S. Pat. No. 6,311,018. This patent discloses placement of optical encodements on film frames, followed by digital removal of the encodements, and restoration of the lost areas of the images. This approach is cumbersome and some image information is lost. The lost information is automatically patched over by replicating neighboring subject matter. With some scenes, the resulting image is distractingly degraded from the original scene. For example, an undesirable loss of information is seen with a human subject or complex background overlapped by an encodement.
A number of methods are known for detecting, from an image, the color of a light source and correcting for the color of the light source. U.S. Pat. Nos. 4,847,680; 4,918,519; 5,659,357 are examples.
It would thus be desirable to provide an improved method for detecting an encodement that can be limited to a central area of a filmstrip, such as the image area.
The invention is defined by the claims. The invention, in broader aspects, provides a photography method, in which a determination is made that a set of captured images includes one or more encoded captured images having a partial shading encodement. The partial shading is partial shadowing or partial filtering or a combination of the two. The encodement has a predetermined edge pattern and is disposed within a predetermined subarea of an image. An encoded captured image is digitized to provide a digital image having a plurality of pixels. A plurality of pixel templates of an edge pattern and the pixels in the subarea of the digital image are convolved to provide a plurality of template position metrics. Each pixel template has the same shape. Each pixel template is differently located in said subarea. The highest of the template position metrics and a predetermined threshold template position metric value of the edge pattern are compared. The digital image is digitally modified with a digital modification preassigned to the partial shading encodement, when said highest template position metric matches the threshold template position metric value.
It is an advantageous effect of the invention to provide an improved method for detecting that an image has been filtered using one of a set of predetermined filters.